1. Field of the Invention
The present invention generally relates to a qubit (quantum bit). More specifically, a qubit is represented by a three-state physical system.
2. Description of the Related Art
The computing power of microprocessors has been doubling every 18 months over the last three decades. This doubling of power has been achieved by reducing the physical size of the basic computing unit, i.e., a transistor. Some of the dimensions of the transistor are currently approaching atomic sizes. At such small dimensions classical physics breaks down and this break down has resulted in a number of problems related to providing computing capability.
The most prevalent problem is the increase in the power requirements for the microprocessor due to a quantum mechanical effect called tunneling, which causes the loss of power. This problem of loss of power is expected to get worse as the dimensions of the transistor are further reduced.
Known Solution
In order to remediate the problem of the breakdown of classical physics at such small dimensions, which thereby translates to the consequent loss of power in a transistor, computers based on quantum physics have been proposed within the industry. Such computers are now known as “quantum computers”.
Quantum computers employ non-intuitive properties of quantum physics. Such properties are not fully understood but can yield extremely powerful computers for the future. An example of such non-intuitive properties in quantum physics is superposition. The principle of superposition implies that a particle can be at two places at the same time. This is in contrast to classical physics, which limits a particle to one place at a given time.
Using this property, scientists have defined a basic computational quantity called the “qubit” (i.e., quantum bit). The qubit has the property that it can store two numbers at the same time, unlike a classical bit, which can store only one number at any given point in time. This property of storing two numbers at the same time in a qubit leads to extremely powerful computers in terms of speed, parallel processing, memory, and physical size of the computer.
It has been shown that these quantum computers can solve computationally complex problems, which are considered intractable using the conventional modern computers. An example of such computationally intensive problem is the factorization of a large number into its prime factors. Such a factorization problem is the key ingredient in encoding of the data for protection from unauthorized reading and use.
Issue Surrounding the Known Solution
Up to now, qubits have been represented by two-state physical systems. Examples of such two state physical systems are a nuclear spin of a hydrogen atom, a photon with two polarizations, a trapped neutral atom with two states, and a trapped ion with two states. In each of these two-state physical systems, the state can be represented as the superposition of the two states. In order to describe such a superposition state, two real numbers, one phase and one magnitude, are needed.
In other words, such a superposition state can store two numbers at the same time and thus represent a qubit.
However, in the conventional representations of a qubit, only one of these two numbers, the magnitude, can be read out easily. It is extremely difficult to read out the second number, namely the phase. Thus, in all of two-state systems studied so far, only in one system (e.g., the trapped ion) has there been demonstrated a control over both numbers. But in this system, scalability to computing devices containing more than two or three qubits has been a huge challenge.
Therefore, a need continues to exist for a design of a qubit having both the capability of storing two numbers and easily reading out two stored numbers while maintaining the property of scalability.